device_info = [
{'device_name':'SW1','mgmt_ip':'10.1.100.101','username':'qytang','password':'qytang'},
{'device_name':'SW2','mgmt_ip':'10.1.100.102','username':'qytang','password':'qytang'},
{'device_name':'SW3','mgmt_ip':'10.1.100.103','username':'qytang','password':'qytang'},
{'device_name':'SW4','mgmt_ip':'10.2.100.104','username':'qytang','password':'qytang'}
    ]
